The installation of decorative tiles (e.g. ceramic, porcelain, stone, or tiles of another material) or stones on a floor or wall includes the steps of adhering the stone or tile to the substrate using a tile-setting adhesive, followed by filling the joints between the individual tiles with a grout material that is plastic (i.e. deformable) in its initial state, but over a short period of time, typically one to 24 hours, becomes a hard and impenetrable mass that permanently fills the joints between the individual tiles. During the installation of the grout, the grout is in a plastic state and is floated or smeared over the tile surface, filling all joints level with the surface of the stone or tile floor or wall covering. After an optional pre-setting period for the grout to develop additional cohesion, the surface of the tile or stone is cleaned with water (sometimes treated with a detergent), leaving the tile or stone surface free of grout and the joints filled with the grout. Grouts provide several functions to the tile floor including supporting the edges of the tile or stone to prevent chipping of the edges, preventing dirt and debris from filling the joints, and providing a decorative appearance since the grouts are often colored to compliment the other colors within an architectural space.
Grouts used for tile or stone installation are often based on hydraulic cement binders such as ordinary Portland cement (OPC) or aluminate or aluminosulfate cements. Grouts based on OPC are used in the majority of applications because of the easy installation properties, excellent durability and low cost. However, OPC-based grouts suffer several deficiencies, including efflorescence, mottling and color variation due to inconsistent curing throughout the grout, poor stain resistance, and poor chemical resistance, especially to acidic chemicals. Grouts based on aluminate or aluminosulfate cements can, depending on formulation, overcome the efflorescence, mottling and color variation; however, they still suffer from poor stain resistance and poor chemical resistance.
Alternatively, the binder in a grout can be based on dispersion polymers, such as polyurethane dispersions (PUDs) or a variety of polyacrylate dispersions. Grouts based on dispersion polymers are color consistent, non-efflorescent and non-mottling. Chemical resistance and stain resistance of these grouts can be good. However, grouts based on dispersion polymers are slower to cure and typically softer in the final cured state relative to cement-based grouts. Also, typical dispersion-based grouts are less resistant to water and tend to soften when continuously submerged.
In a third variety of tile or stone setting grout, the binder is based on thermosetting chemicals such as epoxy resins. Epoxy grouts are typically two-component reactive materials comprised of a first part that contains an epoxy resin and a second part that contains an amine hardener. Also contained in the first or second part are fillers such as sand or fine limestone, rheology modifiers, and coloring agents, to name a few convential components. Alternatively, the fillers, rheology modifiers, and coloring agents may comprise a third component that is added to the first two components. The component that contains the color is usually replicated in multiple colors to provide color alternatives to the architect or designer.
Due to the reactive nature of epoxy grouts, deficiencies observed for hydraulic cement-based grouts and dispersion polymer-based grouts are largely absent. Epoxy grouts are color consistent, non-efflorescing and non-mottling, typically have very good stain resistance, and are resistant to many chemicals depending on the exact epoxy and hardener combinations that are employed. Epoxy grouts cure rapidly to form a hard and durable mass that is insensitive to water. However, epoxy grouts are considered difficult to install, both during the floating process when filling the joints, and afterwards during clean up with water, owing, in part, to their rheology and viscosity and their adhesion to tile and stone surfaces.
To achieve better installation properties, those familiar with the art can formulate epoxy grouts with improved rheology by using water-borne epoxy resins (see for instance U.S. Pat. No. 6,881,768), low viscosity epoxy resins based on bisphenol-epoxy A or bisphenol-epoxy F, or, alternatively, using reactive mono- or di-functional diluents such as C12 and C14 monoglycidylether or 1,4-butanedioldiglycidyl ether available from various manufacturers. The rheology of many commercially available bis-phenol A or bis-phenol F epoxy resins is adjusted by the manufacturer using these reactive diluents prior to their use in epoxy grout formulations.
Better installation properties can also be improved using water soluble amines in the hardener side of the formulation. Amidoamines, or combinations of amidoamines with non-amidoamines, dramatically improve the ability to clean the surface of the tile after floating (filling) the grout into the joints.
These formulation approaches to improve installation properties are well known to those skilled in the art. Unfortunately, the use of viscosity lowering resins or additives, and the use of amidoamines, limits the resistance of epoxy grouts to many chemicals such as organic acids, solvents such as tolune, methyl ethyl ketone, methanol, and xylene, and gasoline. The recent advent of enzymatic cleaners has created a particularly challenging chemical environment in commercial kitchens that utilize deep fat fryers. Oils that splash on the floor are cleaned with the enzymatic cleaners. These so-called “no rinse” cleaners are left to dwell on the floor, giving the enzyme time to break down the oils into the corresponding glycerol and fatty acids. A predominant fatty acid in cooking oils is oleic acid, a monofunctional acid, which is especially degrading to epoxy grouts, requiring the grout used in commercial kitchens to have exceptional oleic acid resistance.
While not wanting to be constrained by theory, it is hypothesized that oleic acid (among others) can undergo transamidation reactions with the amidoamine hardener, thereby leading to non-crosslinking, monofunctional amines.
Thus, epoxy grout formulations that retain relatively good chemical resistance typically have poor installation properties. For this reason, manufacturers of epoxy grouts often produce two product lines (with multiple colors in each line), one product line with good working properties but inferior chemical resistance, and a second that is dedicated for use in environments that require superior chemical resistance such as dairies, breweries, chemical plants, commercial garages, and commercial kitchens. These two product lines have unique epoxy resin and amine hardener parts relative to each other. The product line with easier installation properties contains lower molecular weight epoxy components including reactive diluents, and amidoamines, while the product line with superior chemical resistance utilizes epoxy resins with higher viscosity, without reactive diluents, and does not use amidoamines.
Two full product lines create difficulties for both the manufacturer of the epoxy grout as well as the distributor or seller of the grout. For the manufacturer, maintaining color consistency across two product lines is difficult because the chemical constituents for each grout product line are different and can have different underlying (i.e. unpigmented) appearances, often requiring different coloring components for each product line. Additionally, both the manufacturer and the distributor or seller must maintain two product lines, thereby increasing inventory and the associated space needs and cost.
Thus, there is a need for an epoxy grout system that has excellent chemical resistance while maintaining good installation properties. Additionally, and in order to minimize manufacturing, distribution and display and sale challenges and inefficiencies, there is a need for a grout system that minimizes the number of components over various product lines, each comprising multiple colors, while still providing a variety of well-matched colors that are common to both product lines.